Update step_3b.rkt

step_3b.rkt

@@ -4,7 +4,7 @@
 ;           Group F
 
 ; In this step, we will introduce a form of inheritance, and to do so
-; we have created two new classes : objects and color-points.
+; we have created two new classes : object and color-point.
 
 ; Each class will now have in its state a reference, named super, which
 ; will be pointing to its (unique) parent class.
@@ -20,6 +20,8 @@
 ; it is in this class that we will eventually display if a message
 ; is not understood.
 (define (object)
+  ; Since object is the root of the hierarchy, it has no super value, here represented as a 'nil value.
+  (define super 'nil)
   (define (gettype) 'object)
   (define (self m)
     (cond ((eq? m 'type) (gettype))
@@ -110,7 +112,7 @@
 (display '----------)
 (newline)
 
-; We then test thee creation of two standard points, and verify that
+; We then test the creation of two standard points, and verify that
 ; the different methods from previous steps still work as intended.
 (define p1 (point 1 2))
 (define p2 (point 3 4))